This forum uses cookies
This forum makes use of cookies to store your login information if you are registered, and your last visit if you are not. Cookies are small text documents stored on your computer; the cookies set by this forum can only be used on this website and pose no security risk. Cookies on this forum also track the specific topics you have read and when you last read them. Please confirm whether you accept or reject these cookies being set.

A cookie will be stored in your browser regardless of choice to prevent you being asked this question again. You will be able to change your cookie settings at any time using the link in the footer.

Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
One-wire limits ?
#1
Has anyone run into limits of how many temperature sensors or how long a wire run they can have with one wire ?

Things are starting to get kind of flaky here with 5 or so sensors with maybe 50 feet of wire (guess).
I am using cat 5 wire and have maybe 6 (guess) one to two splitters in the system.
Not all sensors are consistently seen.

A related question, in the 1-wire tab, will selecting 'restart' enumerate the attached devices? I have seen inconsistent behaviour but am not sure if it's the sensor system or if I am not using OpenPlotter correctly.

Has anyone used a dedicated one-wire interface rather than the bit bang approach that the pi uses to get 1-wire data ? The dedicated one-wire interfaces are more sophisticated and allow for longer/bigger one wire setups.
Reply
#2
After a lot of soul and internet searching, I decided to spend a small fortune on a 'linkUSB' which plugs into a USB port and drives a one wire interface. Supposedly, it's active adaptation technology is far superior to the bit banging approach of the pi and I am hoping that I will be able to run a much longer loop.
The unfortunate part - it will no be supported under OpenPlotter's 1-wire tab. I will have to build my own interface to the signalK server (somehow)

On the bright side, at least in theory I should be able to support all the other one-wire goodies that are out there such as switches and more. It won't be pretty, everything will be hard coded as my coding knowledge is woefully inadequate for doing a fancy UI.
Reply
#3
1-wire is originally designed to be used on short distances, e.g. chips on the same board.
It is owned by Maxim (Dallas), and here is their guideline for long lines:
https://www.maximintegrated.com/en/app-n...mvp/id/148

You should be able to drive up to about 200 m total cable length using a simple resistor pull-up according to Maxim.
If you use a 4.7k pull-up resistor, try replacing it with a lower value, e.g. 3.3k, 2.2k, 1.5k or 1k, and see which one works best.
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)